`stack resubmit` printed its whole per-member plan and then refused if the branch had moved, so a refusal read like a completed reconcile to anyone skimming stdout or grepping for `rounds:`. The lease is now taken before the first line, and the message names the local rebase that is the usual way in and `atgc stack sync`. `publish_branch` is split into check/send halves so a caller can do this; the ordinary path is unchanged. Change-Id: I0a99db48586fdf473f05e4e9e7d011447f54e7ac